I. Field
The present application relates generally to wireless communications, and more specifically to methods and systems to facilitate managing cells in a multi-carrier system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, etc.). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), High Speed Packet (HSPA, HSPA+), and others. Moreover, wireless communication systems can be designed to implement one or more standards, such as IS-95, CDMA2000, IS-856, W-CDMA, TD-SCDMA, and the like.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. In such a system, each terminal can communicate with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link can be established via a single-in-single-out (SISO), multiple-in-signal-out (MISO), or a multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min {NT, NR}. Each of the NS independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A MIMO system supports a time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point.
Recent studies have focused on the feasibility of scheduling across two HSDPA carriers. Such research has been particularly focused on utilizing such a scheduling scheme to increase the peak data rates per user and to better utilize available resources by multiplexing carriers in CELL DCH state. This dual carrier approach is commonly referred to as DC-HSDPA (Dual Cell HSDPA or Dual Carrier HSDPA), wherein DC-HSDPA offers both higher resource utilization efficiency and frequency selectivity in order to achieve better performance gains particularly for UEs experiencing poor channel conditions.
Current cell management schemes for DC-HSDPA systems do not allow base stations to take into account downlink conditions as measured by a UE. Such schemes undesirably force base stations perform cell management functions without knowledge of real-time downlink conditions experienced by the UE. It would thus be desirable to have a method and apparatus for facilitating managing cells in a multi-carrier system as a function of downlink measurements taken by the UE.